This application is a continuation of U.S. patent application Ser. No. 14/485,040 filed Sep. 12, 2014, now abandoned, which is a continuation of U.S. patent application Ser. No. 13/013,704 filed Jan. 25, 2011, now abandoned, which claims the benefit of priority of U.S. Provisional Patent Application No.61/299,794, filed Jan. 29, 2010, in which each application is incorporated by reference in their entirety.
The present invention relates generally to biosynthetic processes, and more specifically to organisms having p-toluate, terephthalate or (2-hydroxy-3-methyl-4-oxobutoxy)phosphonate biosynthetic capability.
Terephthalate (also known as terephthalic acid and PTA) is the immediate precursor of polyethylene terepthalate (PET), used to make clothing, resins, plastic bottles and even as a poultry feed additive. Nearly all PTA is produced from para-xylene by oxidation in air in a process known as the Mid Century Process. This oxidation is conducted at high temperature in an acetic acid solvent with a catalyst composed of cobalt and/or manganese salts. Para-xylene is derived from petrochemical sources and is formed by high severity catalytic reforming of naphtha. Xylene is also obtained from the pyrolysis gasoline stream in a naphtha steam cracker and by toluene disproportion.
Cost-effective methods for generating renewable PTA have not yet been developed to date. PTA, toluene and other aromatic precursors are naturally degraded by some bacteria. However, these degradation pathways typically involve monooxygenases that operate irreversibly in the degradative direction. Hence, biosynthetic pathways for PTA are severely limited by the properties of known enzymes to date.
A promising precursor for PTA is p-toluate, also known as p-methylbenzoate. P-Toluate is an intermediate in some industrial processes for the oxidation of p-xylene to PTA. It is also an intermediate for polymer stabilizers, pesticides, light sensitive compounds, animal feed supplements and other organic chemicals. Only slightly soluble in aqueous solution, p-toluate is a solid at physiological temperatures, with a melting point of 275° C. Microbial catalysts for synthesizing this compound from sugar feedstocks have not been described to date.
Thus, there exists a need for alternative methods for effectively producing commercial quantities of compounds such as p-toluate or terephthalate. The present invention satisfies this need and provides related advantages as well.